Method for assembly of evaporator tubing to liner

ABSTRACT

A method and apparatus for assembling tubing to a supporting and heat exchanging wall for heat transfer therebetween by which the tubing is prepostioned on the wall and held by a releasable holding force until an adhesive or cementitious binder material permanently secures the tubing to the wall with sufficient strength to retain the tubing in the desired position after removal of the holding force. In refrigeration apparatus, evaporator tubing may be assembled on the exterior walls of a boxlike liner by temporarily holding it in position with a magnetic field provided by a magnet carrying male fixture formed to fit the interior of the liner, coating the liner exterior and tubing with a binder such as by dipping it in a molten thermoplastic and allowing the thermoplastic to set by cooling, and removing the male fixture.

March 26, 1974 N. GRIFFITHS 3,799,331

METHOD FOR ASSEMBLY OF EVAPORA'I'OR TUBING TO LINER 2 Sheets-Sheet 1 Filed Dec. 1, 1971 INVENTOR. 1 4654/5 M. QP/FF/r/As BY MQ/EA/A/g FA'QIQ/A/GIOM PEflKA/f #50 00 March 1974 N. GRIFFITHS METHOD FOR ASSEMBLY OF EVAPORATOR TUBING TO LINER 2 Sheets-Sheet 2 Filed Dec. 1, 1971 INVENTOR.

4654/5 M Gfl/FF/THS BY Mn/En/A/K Knee/Mar y United States Patent O 3,799,831 METHOD FOR ASSEMBLY OF EVAPORATOR TUBING T LINER Leslie N. Grifliths, Tarvin, England, assiguor to Kelvinator, Inc., Grand Rapids, Mich.

Filed Dec. 1, 1971, Ser. No. 203,590 I Int. Cl. B32b 31/00; C09j 3/30,- B28f N32 US. Cl. 156-297 6 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for assembling tubing to a supporting and heat exchanging wall for heat transfer therebetween by which the tubing is prepositioned on the wall and held by a releasable holding force until an adhesive or cementitious binder material permanently secures the tubing to the wall with suflicient strength to retain the tubing in the desired position after removal of the holding force. In refrigeration apparatus, evaporator tubing may be assembled on the exterior walls of a boxlike liner by temporarily holding it in position with a magnetic field provided by a magnet carrying male fixture formed to fit the interior of the liner, coating the liner exterior and tubing with a binder such as by dipping it in a molten thermoplastic and allowing the thermoplastic to set by cooling, and removing the male fixture.

(FIELD OF THE INVENTION This invention concerns the manufacture of heat exchanger wall panels such as found in refrigeration cabinets and, in particular, relates to a method and apparatus for assembling refrigeration tubing to a supporting and heat exchanging wall.

The invention is particularly adapted to be used in assembling evaporator tubing to the liner or inner wall of refrigeration apparatus such as a refrigerator, freezer, or cooler. Evaporator tubing is normally arranged in contact with the liner along its length so that evaporation of refrigerant in the tubing extracts heat through the liner to cool the interior of the apparatus.

DESCRIPTION OF THE PRIOR ART According to a previous method of assembling evaporator tubing to a liner, tubing, usually arranged in continuous coils, is positioned over the exterior surface of the liner and fastened at intervals with bridge-like clips spot welded to the exterior surface of the liner. Besides permanently holding the tubing on the liner, the clips serve to conduct heat between the liner and tubing.

Steel evaporator tubing, widely used because of its relatively low cost, is subject to corrosion and must be protectively coated after fastening steel tubing with the clips, for example, the outer surfaces of the resulting assembly of the tubing and liner are protected from moisture and corrosion by dipping the assembly into a tank of bitumen in a molten state at an elevated temperature. The assembly is removed from the tank with a generally uniform coating of bitumen on its exterior and is subsequently allowed to cool before further use.

Besides the labor required to position and weld clips onto the liner, this prior method of fastening the tubing has the disadvantage of not being well suited for use with various liner materials, such as aluminum, which are relatively difficult to weld.

SUMMARY OF THE INVENTION The invention provides a method and apparatus for temporarily holding refrigeration tubing on a supporting and heat exchanging wall. Tubing is held in substantially uniform heat exchanging contact with the wall by a re- 3,799,831 Patented Mar. 26, 1974 ice leasable magnetic field until the tubing is permanently cemented into position on the wall. Preferably, in accordance with the invention, the coating material used to permanently cement or adhere the tubing to the wall is, at the same time, used to protect the tubing and wall from corrosion.

In the preferred embodiment, a thermoplastic material, such as bitumen, is provided in a molten condition. Tubing is arranged on a refrigeration wall and held in a desired position by the magnetic field. The assembly, including the source of the magnetic field, may be dipped into the molten thermoplastic and then removed and allowed to cool to provide a substantially uniform coating on the wall and tubing which permanently holds these members in contact. It has been found that heat conduction between the tubing and wall assembled in this manner is substantially the same as that resulting from the prior welded clip assembly method.

The refrigeration walls may be assembled in the form of a boxlike structure or liner having at least one open side. A suitable magnetic field for temporarily holding evaporator tubing on the sides of the liner box is produced according to the invention by arranging permanent magnets in a fixture constructed to fit into the liner box through its open side. The magnet supporting fixture is a male form dimensioned to fit into the liner box. The fixture supports a plurality of permanent magnets parallel to and slightly inward from the planes of its walls to produce a uniform holding force and to prevent removal forces from becoming excessive. According to one embodiment of the invention, the magnets may be retractably mounted on the support fixture to substantially eliminate any magnetic attraction between the magnet, liner, and tubing during insertion and withdrawal of the supporting structure.

A principal advantage of the invention is the reduction of the manufacturing cost of tubing and liner assemblies by eliminating labor and equipment associated with previously used methods of assembly. Additionally, the invention permits the use of any practical liner material since it is not limited to easily welded materials nor is it limited to magnetic materials.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the liner, evaporator tubing, and a magnetic core assembly in vertical alignment with a dipping tan'k.

FIG. 2 shows a finished liner assembly produced fromevaporator tubing and a liner such as shown in FIG. 1.

FIG. 3 is a fragmentary cross sectional view of the evaporator liner assembly taken along the line 3-3 indicated in FIG. 2.

FIG. 4 is a perspective view of a finished liner assembly similar to that shown in FIG. 2 but with a different evaporator coil configuration.

'FIG. 5 shows a second embodiment of a magnetic core assembly similar to that shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, FIG. 1 shows a liner assembly 10 for a refrigeration apparatus and, immediately below it, evaporator tubing 11 adapted to be positioned around the liner assembly. The linear assembly 10 is a boxlike structure having end sidewalls 13 and 14 and sidewalls 15 and \16. The upper side of the boxlike liner assembly 10, as viewed in FIGS. 1, 2, and 4, is open while the opposite side is provided with a bottom wall 18. Each wall or panel 13-16 is constructed of sheet material with its edges turned over to form either a tongue or an interengaging groove at a junction 19 between abutting edges sidewalls 13-16, bottom wall 18, and the open side of the liner assembly define the general shape of a polyhedron having its opposed sides parallel to one another and adjacent sides perpendicular.

The evaporator tubing 11 is preferably formed of steel or other magnetically attractable material and comprises a plurality of straight tube portions 26 adapted to run long each sidewall 13-16 of the liner assembly 10. These generally straight tubing portions 26 are normally continuous with one another and form a basketlike structure which may be fitted over the liner assembly 10.

A magnetic core assembly 31, constructed in accordance with the invention, is illustrated in the upper portion of FIG. 1. The magnetic core assembly 31 has a rectangular blocklike structure which is adapted to fit into the interior of the liner assembly -10 with a slight clearance. The magnetic core assembly 3-1 comprises a support structure 32 and a plurality of spaced magnet assemblies 33 supported thereon. As shown in FIG. 1, the support structure 32 is similar in form to a cage and comprises a plurality of spaced vertical supports 36 and vertical end members 37. These vertical elements 36 and 37 are held in position by suitable longitudinal frame members 38 and crossover frame members 39 at the upper and lower portions of the support structure 32. Preferably, the members 36-39 comprising the support structure 32 are formed of a non-magnetic material such as wood to prevent magnetic interaction between the support structure 32 and the magnets 33.

The magnet assemblies 33 each comprise, preferably, a plurality of permanent horseshoe type magnets 42 in vertical alignment and secured to a pair of steel poles 43- and 44. The horseshoe magnets 42 of each magnet assembly 33 are aligned according to polarity with the north pole of each horseshoe magnet 42 contacting a common vertical pole 43 and the south pole of each contacting the opposite pole 44. The permanent magnet assemblies 33 intervene between the spaced vertical supports 36 of the support structure 32. The magnet assemblies 33 are pivotally mounted on adjacent vertical supports 36 with hinges 48 suitably fastened on the vertical supports 36 and on one of the elongated vertical poles 44. Each elongated vertical pole 43 and 44 of the permanent magnets 33 provides a face 46 and 47 which lies slightly inward of the outer faces of the vertical supports 36 When the magnets 33 are in their extended or operative positions. Thus, when the magnetic core 31 is positioned in the liner assembly 10, these faces 46 and 47 do not touch the liner so that high retraction or stripping forces are not required to remove or retract these magnets from their operative positions.

There is provided a dipping tank 52 containing, preferably, molten thermoplastic material 53 such as bitumen and being sufficiently large to fully receive the liner assembly 10 with the evaporator tubing 11 secured to the exterior of its sidewalls 13-16 by the magnetic core assembly 31 in a manner described below.

In reference to the embodiment illustrated in FIG. 1, the procedure for permanently assembling the evaporator tubing 11 to the liner assembly 10 begins with the prepositioning of the evaporator tubing on the liner assembly '10. With thcmagnet assemblies 33 all in a retracted position such as that occupied by the magnet assembly 33a, the magnetic core assembly 31 is lowered into the liner assembly 10 by a hoist or the like. In their retracted positions, all parts of each magnet assembly 33 are at least about /2 inch away from the line 10. The magnet assemblies 33 are then all moved manually or with suitable power means into their operative positions parallel to and confronting the inner sides of the liner sidewalls 13-16. Ideally, the magnetic poles 46 and 47 of each magnet 33 extend in a direction transverse to the longitudinal direc- -"tion of the lengths or portions 26 of the evaporator tubing 11 to maximize the magnetic attraction and uniformly hold each portion 26.

Magnets suitable in magnetic strength pull the tubing portion 26 into continuous contact with the exterior sides of the liner sidewalls or panels 13-16. It may be apprecited that, owing to the magnetic permeability of steel, the evaporator tubing 11 will be more tightly held against the Walls of the liner assembly 10 if they are constructed of steel rather than of a non-magnetic material. Nevertheless, it has been found that commercially available permanent magnet assemblies are adequate in strength to satisfactorily hold steel evaporator tubing in intimate continuous contact with aluminum liner sidewalls. A specific example of a suitable magnet assembly is a Magna Rail type 31-3 available from South Wales Eriez Magnetics of Blackwood Mon. U.K. This magnetic assembly has a magnetic strength sufiicient to hold a steel test bar 0A2" x 1" x 3") through a A" thickness of rubber placed on the face of the magnet, with a force of approximately 78 ounces.

With the magnetic core 31 securely holding the evaporator tubing 11 on the liner sidewalls 13-16, the core 31, liner 10, and tubing 11 are lowered into the tank 52 of molten bitumen 53 until substantially all of the tubing is immersed. The magnetic core 31 may be weighted with suitable material to facilitate immersion of the liner 10 to the correct depth. The magnetic core 31, liner 10, and tubing 11 are subsequently withdrawn from the tank carrying a bitumen coating 58, to A thick, for example, on the exterior of the liner and tubing. The coating is allowed to set by cooling for a period of time before the magnets 33 are retracted and the magnetic core 31 is withdrawn. The resulting evaporator tubing and liner assembly, designated 55, is shown in FIG. 2. FIG. 3 shows a portion of the liner and tubing assembly 55 in cross section. As shown, the outer surface 56 of the liner sidewall 16 and the outer surface, designated 57, of each length of tubing 26 are fully covered by the bitumen coating.

While the number of materials adapted to permanently adhere or cement the tubing 11 to the liner 10 is practically unlimited, it has been found that, owing to the protection it affords as a permanent barrier against corrosion of the tubing under adverse moisture conditions, bitumen is particularly suited for this application. A specific example of such as substance is a blow oxidized grade of bitumen supplied by Shell-Mex and B. P. Ltd., of London, England having the following properties determined according to Test Methods for Bitumen, British Standard 3235, British Standards Institution, and marketed under the trade name Mexphalte with the grade name R-40:

MEXPHALTE BITUMEN Grade name: R85/40 Penetration at 25 C. (77 F.) 35/45 Softening point (R & B) C 80/90 Softening point (R & B) F 176/194 Ductility (cms.) at 15 C. (59 F.) min. Ductility (cms.) at 25 C. (77 F.) min. 3 Loss on heating percent wt. 5 hrs. at 163 C. (325 F.) max. 0.5 Drop in penetration after heating percent max. Flash point (Cleveland Open Cup) C.

min. 200 Flash point (Cleveland Open Cup) F.

min. 392 Solubility of carbon disulphide and wt.

min. 99.5 Ash content percent wt. max. 0.5

Specific gravity at 25/25 C. (77/77 F.) LOO/1.05 Temperature of dipping tank 180 C. Temperature of dipping tank 365 -F.

With this example, dipping usually lasts in order of two minutes and cooling of the order of five minutes when the bath temperature is approximately 150 F. above its melting point i.e. 176 to 194 F. Other suitable nonmetallic organic materials, besides bitumen, may, of course, be used as a medium to bind, by adhering, or cementing, or the like, the tubing to the liner walls.

FIG. 4 shows a liner and tube assembly 66 similar to the assembled article 55 of FIG. 2 but with a different tubing arrangement. In this construction, evaporator tubing is arranged in continuous substantially straight portions 67 which, for the most part, do not extend around the corners of the liner. The continuous straight portions 67 form coils which are referred to as the panel type. These coils may be placed in position after the magnetic core 31 has been placed in the liner.

FIG. 5 illustrates another embodiment of a magnetic core assembly 71 in accordance with the invention which differs from the embodiment as shown in FIG. 1 in that the permanent magnets, designated 73, are non-retractable relative to the support structure, designated 74. The construction of the magnetic core 71 is similar to that described above for the magnetic core 31 having retractable magnets 33. The support structure 74 is preferably formed of wood or other non-magnetic material and comprises a plurality of vertical spaced panels 76 and a plurality of horizontal spaced stringers 77 suitably fastened to the vertical panels 76. The magnets 74 each comprise a pair of elongated vertical steel poles 78 and 79 secured to the stringers 77 with screws 81. Horseshoe magnets 82, magnetizing the poles 78 and 79, extend through the spacing between the horizontal stringers 77 while the poles 78 and 79 lie in the spaces between the vertical panels 76. Here, as in the operable position of the magnets 33 of the embodiment of FIG. 1, the outer faces of the magnet poles 78 and 79 are slightly inward of the planes containing the vertical panels 76. This magnetic core 71 is used in the same manner as that described above with the exception that the magnets are not retracted or extended relative to the support structure 74. Under ordinary circumstances, this somewhat simplified embodiment of the magnetic core has proven to be satisfactory in use.

The foregoing description is necessarily detailed in character so that the invention may be completely set forth, but it will be understood that modifications may be made in its construction and details without departing from the principles and spirit of the invention.

What is claimed is:

1. A method of assembling tubing to a refrigeration panel comprising the steps of temporarily holding a plurality of steel tube portions on a panel with a longitudinal section of each tube portion in longitudinal alignment and in substantially continuous direct contact with one side of the panel for heat conduction therebetween with a magnetic field produced by a magnet disposed on the other side of the panel, coating a settable adhesive material over both said plurality of tube portions and the panel adjacent the areas of contact between the tube and panel, and removing the magnetic field after said adhesive material is in a self-suflicient condition to retain the plurality of tube portions in substantially the same position in which they are held by said magnetic field.

2. An assembly method as set forth in claim 1 wherein said adhesive material is applied as a uniform coating on said tube portions and said panel to protect said tube portions and panel from corrosion.

3. An assembly method as set forth in claim 2 wherein said adhesive material is a settable liquid and is applied to said tube portions and said panel by immersing both in said material.

4. An assembly method as set forth in claim 2 wherein said adhesive material is a thermoplastic being a liquid at elevated temperatures and substantially a solid at room temperature, and said adhesive material is applied to said tube portions and said panel while the material is in its liquid state.

5. A method for assembling steel evaporator tubing to a panel of a rectangular boxlike liner of a refrigerator apparatus comprising the steps of positioning a plurality of steel tube portions on the exterior side of a liner panel in a desired pattern, temporarily holding said steel tube portions along their length in substantially continuous direct heat conducting contact with the exterior side of the liner panel by a magnet disposed along the interior side of the liner panel, coating both said steel tube portions and liner panel with a thermoplastic by dipping the liner with the steel tube portions held thereon by said magnet into a tank containing the thermoplastic at an elevated temperature sufficient to make it liquid, withdrawing said tubing and liner from said tank with a thermoplastic coating thereon, allowing the thermoplastic coating to cool and harden sufficiently to retain said steel tubing portions in substantially the same position in which said magnet holds them, and subsequently removing said magnet from the interior of said liner.

6. A method of assembly as set forth in claim 5 wherein the steel tube portions are in parallel alignment in one direction and said magnet is provided with poles extending in a direction perpendicular to said one direction.

References Cited UNITED STATES PATENTS 2,856,163 10/1958 Bidak et al. -171 2,579,898 12/1951 Brucker 165-169 X 3,442,094 5/1969 Rush et al. 62-516 2,713,379 6/ 1955 Sisson 269-8 2,795,035 *6/1957 Kafer 165-171 X 1,624,538 4/1927 Crain 269-8 X 1,967,031 7/1934 Lee 117-113 X 2,346,193 4/ 1944 Simmons 269-8 UX 2,927,877 3/1960 Norman 156-305 X 3,033,144 5/1962 Schmidt 269-8 3,246,120 4/ 1966 Brandenburg 165-171 X ALFRED L. LEAVIIT, Primary Examiner T. E. ROKAN, Assistant Examiner US. Cl. X.R.'

UNE'ETED S'ZYNEE-lffi PfiffiiilfQ'i'. 0'1 FRY-E1 CE EJE EEA'KE 6} E? QQRREG'EEGN Patent" No. '3 799 831. Dated MIrCh Z6 1974 t fls) eslie N. Griffiths It is certified that: error appcar in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 65, change "linear" to' "liner".

C0lumn'3 line 11, change "long" to. "along"; and

1ine 71, change "line"to "linei'".

Column 4, line 6, change "portion 2 6 to --portions 26 I lines and 8, change "'appreitd" 9 7 "appreciated-e;

' line 48, change "s" to --a-; I

line 48, change "blqw" to --b 1o;wn--; and

line 70, change and wt." to percent. wt.-

' I, Column 5, line 28, change magnets 74" to ,-mag ne ts 73--.

Signed and saled this 3rd day of Dec ember 1974.

(SEAL) Attest: V I

MCCOY M. GIBSON JR. 1 C. MARSHALL DANN Attesting Officer Commis'sloner of Patents FORM Po-wsouo-sm v 

